The present invention relates to a material that is capable of forming a pattern of the order of nanometers in a self-organized manner on a substrate, the pattern being utilized as a mask for forming a nanopattern excellent in regularity. The present invention also relates to a material that is capable of forming a bulk structure of the order of nanometers in a self-organized manner, the structure being utilized as it is as a nanostructure of high regularity, or utilized as a template for forming another nanostructure of high regularity. The material of the present invention is applied for manufacturing a magnetic recording medium for hard disks having a recording density of 10 Gbit/inch2 or more, an electrochemical cell, a solar cell, a photovoltaic device, a light emitting device, a display, a light modulating device, an organic FET device, a capacitor, a high-precision filter, etc.
Needs for a fine pattern or structure are increasingly desired, as improvement in performance of electronic parts. In the electronic parts such as LSI and liquid crystal display, for example, micro-fabrication techniques are required. Many devices such as an electric cell and a capacitor are required small volume and large surface area. In future, a high-density three-dimensional packaging will be needed. Lithography is employed in these processes, and thus the manufacturing cost becomes higher as more micro-fabrications are needed.
On the other hand, there is a technical field where precision as high as in the case of the lithography is not needed, although a patterning of the order of nanometers is required. However, a simple patterning method has not known hitherto, there is no other choice to form a fine pattern by lithography using an electronic beam or deep ultraviolet ray in such a technical field. As mentioned above, in the lithography technique, operations are complicated and enormous investment is required as the processing dimension becomes smaller.
Under these circumstances, as a simple pattern forming method alternative to the lithography technique, a method utilizing a structure having micro polymer phases formed in a self-developed manner from a block copolymer.
For example, P. Mansky et al. have reported, in Appl. Phys. Lett., Vol. 68, No. 18, p.2586-2588, a method in that a sea-island type microphase-separated film made of a block copolymer of polystyrene and polyisoprene is formed on a substrate, the polyisoprene is decomposed by ozonation and removed to form a porous film, and the substrate is etched using the porous film as a mask, thereby forming a pattern, to which the structure having micro polymer phases is transferred, on the substrate. In addition, M. Park et al. have reported, in Science, Vol. 276, 1401-1406, a method in that a sea-island type microphase-separated film made of a block copolymer of polystyrene and polyisoprene is formed on a substrate, the polyisoprene phase is doped with osmium oxide by a vapor phase reaction to improve etch resistance, and a pattern is formed using the polyisoprene phase selectively doped with osmium oxide as a mask.
Such a method using the microphase separation of the block copolymer is simple and inexpensive as compared with the lithography technique. However, the ozonation is complicated as well as needs relatively long reaction time, so that it is difficult to improve throughput. Also, since the osmium oxide has high level of toxicity, it is scarcely used in general purpose from the viewpoint of safety.
An object of the present invention is to provide a pattern forming material and a method for forming a pattern, which show high process throughput and capable of forming very easily a planar pattern or three-dimensional structure of the order of nanometers having considerable regularity.
A still another object of the present invention is to provide a method for manufacturing easily a magnetic recording medium, a field emission display, a field emission cathode, a separator and electrode for an electrochemical cell, a catalytic electrode for a fuel cell, a filter, etc., by making use of the aforementioned material.
A pattern forming material according to the present invention comprises a block copolymer or graft copolymer having two polymer chains whose ratio between N/(Ncxe2x88x92No) values of respective monomer units is 1.4 or more, where N represents total number of atoms in the monomer unit, Nc represents the number of carbon atoms in the monomer unit, No represents the number of oxygen atoms in the monomer unit.
The block copolymer or graft copolymer satisfies the conditions is typically that having a polymer chain containing aromatic rings and an acrylic polymer chain.
A pattern forming material of the present invention contains a block copolymer or graft copolymer having a polysilane chain and a carbon-based organic polymer chain.
A method for forming a pattern of the present invention comprises steps of: forming a molded product made of an above-mentioned pattern forming material; forming a structure having micro polymer phases in the molded product; and dry-etching the molded product to remove selectively a polymer phase from the structure having micro polymer phases, thereby forming a porous structure.
A method for forming a pattern of the present invention comprises steps of: forming a film made of an above-mentioned pattern forming material on a substrate; forming a structure having micro polymer phases in the film; selectively removing a polymer phase from the structure having micro polymer phases formed in the film by dry-etching; and etching the substrate using remaining another polymer phase as a mask, thereby transferring the structure having micro polymer phases to the substrate.
A method for forming a pattern of the present invention comprises steps of: forming a pattern transfer film on a substrate; forming a film made of a pattern forming material comprising a block copolymer or graft copolymer having two polymer chains whose ratio between dry etch rates is 1.3 or more on the pattern transfer film; forming a structure having micro polymer phases in the film; selectively removing a polymer phase from the structure having micro polymer phases formed in the film by dry-etching; etching the pattern transfer film using remaining another polymer phase as a mask, thereby transferring the structure having micro polymer phases to the pattern transfer film; and etching the substrate using the pattern transfer film as a mask to which the structure having micro polymer phases is transferred, thereby transferring the structure having micro polymer phases to the substrate.
Another pattern forming material of the present invention contains a block copolymer or graft copolymer having a polymer chain whose main chain is cut by irradiation with an energy beam and an indecomposable polymer chain against irradiation with an energy beam.
An electron beam is typically used as the energy beam. The polymer chain whose main chain is cut by irradiation with the energy beam is typically an acrylic chain substituted by a methyl group or halogen at xcex1-position or a polysilane chain.
A method for forming a pattern of the present invention comprises steps of: forming a molded product made of an above-mentioned pattern forming material; forming a structure having micro polymer phases in the molded product; irradiating the molded product with an energy beam, thereby cutting a main chain of a polymer phase in the structure having micro polymer phases; and selectively removing the polymer chain whose main chain is cut by development or etching, thereby forming a porous structure consisting of remaining another polymer phase.
A method for forming a pattern of the present invention comprises steps of: forming a film made of an above-mentioned pattern forming material on a substrate; forming a structure having micro polymer phases in the film; irradiating the film with an energy beam, thereby cutting the main chain of a polymer phase in the structure having micro polymer phases; selectively removing the polymer chain whose main chain is cut from the structure having micro polymer phases by etching; and etching the substrate using remaining another polymer phase as a mask, thereby transferring the structure having micro polymer phases to the substrate.
A method for forming a pattern of the present invention comprises steps of: forming a pattern transfer film on a substrate; forming a film made of an above-mentioned pattern forming material on the pattern transfer film; forming a structure having micro polymer phases in the film; irradiating the film with an energy beam, thereby cutting the main chain of a polymer phase in the structure having micro polymer phases; selectively removing the polymer chain whose main chain is cut from the structure having micro polymer phases by etching; etching the pattern transfer film using remaining another polymer phase as a mask, thereby transferring the pattern of the structure having micro polymer phases to the pattern transfer film; and etching the substrate using the pattern transfer film to which the pattern of the structure having micro polymer phases is transferred as a mask, thereby transferring the structure having micro polymer phases to the substrate.
A still another pattern forming material of the present invention comprises a block copolymer or graft copolymer comprising: a polymer chain comprising a repeating unit represented by the following formula: 
where R1 and R2 independently represent a substituted or unsubstituted alkyl group, aryl group aralkyl group or alkoxyl group having 1 to 20 carbon atoms, and a thermally decomposable polymer chain.
The thermally decomposable polymer chain is typically a polyethylene oxide chain and a polypropylene oxide chain.
A method for forming a pattern of the present invention comprises steps of: forming a film made of a pattern forming material comprising a block copolymer or graft copolymer having at least one thermally decomposable polymer chain on a substrate; forming a structure having micro polymer phases in the film; removing the thermally decomposable polymer phase from the structure having micro polymer phases by heating to a thermal decomposition temperature or more; etching the substrate using remaining another polymer phase as a mask, thereby transferring the pattern of the structure having micro polymer phases to the substrate.
A method for forming a pattern of the present invention comprises steps of: forming a pattern transfer film on a substrate; forming a film made of a pattern forming material comprising a block copolymer or graft copolymer having at least one thermally decomposable polymer chain on the pattern transfer film; forming a structure having micro polymer phases in the film; removing the thermally decomposable polymer phase from the structure having micro polymer phases by heating to a thermal decomposition temperature or more; etching the pattern transfer film using remaining another polymer phase as a mask, thereby transferring the pattern of the structure having micro polymer phases to the pattern transfer film; etching the substrate using the pattern transfer film as a mask, to which the pattern of the structure having micro polymer phases is transferred, thereby transferring the pattern of the structure having micro polymer phases to the substrate.
A method for forming a pattern of the present invention comprises steps of: forming a molded product made of a pattern forming material comprising a block copolymer or graft copolymer having at least one thermally decomposable polymer chain; forming a structure having micro polymer phases in the molded product; removing the thermally decomposable polymer phase by heating to a thermal decomposition temperature or more, thereby forming a porous structure consisting of remaining another polymer phase; and filling pores of the porous structure with an inorganic material.
An electrochemical cell of the present invention comprises a pair of electrodes and a separator interposed between the electrodes and impregnated with an electrolyte, wherein the separator is constituted by a porous structure formed by selectively removing a polymer phase from a block copolymer or graft copolymer having a structure having micro polymer phases.
An electrochemical cell of the present invention comprises a pair of electrodes and an electrolyte layer interposed between the electrodes, wherein at least a part of the electrodes is constituted by a porous structure formed by selectively removing a polymer phase from a block copolymer or graft copolymer having a structure having micro polymer phases. The porous structure typically made of carbon.
A hollow fiber filter of the present invention is made of a porous structure formed by selectively removing a polymer phase from a block copolymer or graft copolymer having a structure having micro polymer phases.
A method for manufacturing a porous carbon structure of the present invention comprises steps of: mixing a precursor of thermosetting resin, a surfactant, water and oil, thereby preparing a microemulsion in which colloidal particles containing the precursor of thermosetting resin are dispersed; curing the precursor of thermosetting resin unevenly distributed in the colloidal particles; removing the surfactant, water and oil from the colloidal particles, thereby providing porous structures of cured thermosetting resin; firing to carbonize the porous structures.
A still another method for forming a pattern of the present invention comprises steps of: applying a blend of a polymer including a metal particle and a block copolymer or graft copolymer to a substrate to form a film; forming a structure having micro polymer phases in the film and segregating the metal particles covered with the polymer in a central portion of a polymer phase or at an interface between the polymer phases in the block copolymer or the graft copolymer; selectively or entirely removing the polymer phases by etching in which the metal particles are segregated, thereby leaving the metal particles.
The method is suitably applicable to magnetic recording medium by depositing a magnetic material on the remaining metal particles. Also, the method is suitable applicable to manufacture of a field emission by depositing a conductor or semiconductor on the remained metal particles to form emitters.
A method for manufacturing a capacitor of the present invention comprises steps of: forming a film made of a blend of a polymer including a metal particle and a block copolymer or graft copolymer; allowing the film to form a lamella structure having micro polymer phases and segregating the metal particles covered with the polymer in a central portion of each polymer phase in the lamella structure; and aggregating the metal particles to form a metal layer in the central portion of each polymer phase in the lamella structure.
A method for manufacturing a catalytic layer of a fuel cell of the present invention comprises steps of: forming a film made of a blend of a block copolymer or graft copolymer including a metal particle and a block copolymer or graft copolymer; forming a structure having micro polymer phases in the film and segregating the metal particles covered with the polymer at an interface between the polymer phases forming the structure having micro polymer phases; and selectively removing a polymer phase in the structure having micro polymer phases, thereby leaving the metal particles on a surface of remaining another polymer phase.